The methods is suitable for homogeneous soil. In this method a hole is made in the soil below a water table with the help of post hole digger. The water level in the bore is allowed to come in equilibrium with the water table in the soil and the water is pumped out from the bore. The rate of rise of water in the bore is recorded and the hydraulic conductivity is calculated with the following formula
when auger hole is drilled upto the impermeable layer (3)
a = hole radius A t = time in seconds, yo - initial water level in cm, yi = final water level in cm,
K = hydraulic conductivity in meter/second, d = distance from bottom of the hole to water table and
S = constant of proportionality which is a distance from bottom of the hole to the impermeable layer and is equal to ad/0.19.
Ernst’s method for layered soils
In this method two auger holes Bi and B2 of different depths are made in the soil. The bottom of the first hole is kept 10 cm above the second layer. The second hole should be deep enough in the lower layer. The entity (d-h) should be greater than 15.
The conductivity in the first hole, KI is determined as usual. The mean conductivity K is determined for two layers by recording rate of rise in the second hole. Hydraulic conductivity in the 2nd layer, K2 is then calculated by the following relationship.
K1 and K2 = hydraulic conductivity of 1st and 2nd layer, respectively.
K = mean hydraulic conductivity of two layers
D1 and d2 == distance between water table and bottom of the lsl and 2nd bore, respectively. The results are satisfactory if K2 is greater than K1
Child method with two auger holes
Two auger holes, Wi and W2 of equal diameter and depth, are made below the water table. Water from W, is pumped out and poured into w2 to create a difference in hydraulic head A H. Hydraulic conductivity K is then calculated as follows-
Q = rate of pumping,
A H = hydraulic head difference between the two holes,
L = depth of the hole below the water table, a = radius of the hole,
b = distance between the two holes,